Method of inhibiting hydrogen sulfide corrosion of metals



Patented:Mayy 3, .1952

a f I,

22596.42 MELEHGDQE INHIBVITINQJIQXDROGEN CDRRO SIONOF METALS'.- Melvin-i1.lMoyertlawrence; Kansi, Joseph-M .HershrfEoi-t Hills; N. Y.,...assignors'tdf(lltie .serviceiilompann Battle'svillaklm,ancre .asian-na (o1. 23a-8.55)

Qur invention relates toy an improved method rif/inhibitingV corrosion of metaL. andds-more patti'cularly concerned with; the trezaitment@0.15.ahydrogen sulide containing. brines'A of 'theitype obytained in theproduction of crude-foilto ,reduce their corrosive effects upon. oilproduction and transmission equipment.

This application is a-division of ouriccpending application Serial No. 773-,506,;led1September 111, 1947 now U. S. Patent 2,496,354.

The corrosive action v of oilfeldzbrines containing hydrogen sulfide in solutionahaslongv been recognized as asourceof` very:` substantialplosses in oil production equipment. Inxsome elds,,for example, the i brine which is :taken outv wit-,h1 the oil is so corrosive in its nature as to'zbe capable'sof destroying the Well' tubing Within avmatteizfofa very few months; and the- Well casings',sepa-r rators, pumps, and other-equipment Withfwhich such mixtures comednto contact'..haaafeoms parably short life. It' has been 'thef-practiceeto utilize caustic soda, soda asli,a11`d"- other' alkaline compounds for neutralizing theV acidic 4cornfponents of brines ofV this. general: character; and of thereby limiting their corrosive.-v action; These neutralization treatments; i however, ;re.' quire the use of comparatively;largefamountszof the inhibiting agents, arefcorrespondingly costly; and from a long range pointof View, lhavefnot been outstandingly successful.

The primary object-of ourinventionvisfto provide an improved process for tprotecting metals,` and particularly iron and steelrequipmenunsed in the handling of crude oil in-:thepresence-of the highly corrosive typesv of. bridesIrequentlyen-r countered in oil fields.

We have discovered that oil wellxtubing; and casings, as Well as other equipment used irr oil production,v may be'substantiallyY and effectively protected against corrosive`4 .actionof connate. brines by mixing with the latter;Y an 'organic' amino-reactive compound '.Whichsser-vesrasn-af corrosion inhibitor. In general-We .have 4Lfoune'tthat. the heterocyclie amino-reactive.L compounds, -thealkyl and alkanol amine-aldehyde condensation productsof both cyclic andnoncyelic-typesaandl the alkyl-ureasare effective. for'our purposes.

In accordanceY with our inventiony .wel inject a suitable quantity of a selected inhibitor.y com-- pound into an oil well and therebymingleitwith1 the oil-brine production` so thatthe mixture comes into contact with:the\velltubing; casingr and other producingequipment. 'lllhuswer-,mayvt introducethe inhibitor into-the toploffthe casinge so that it flows down into the well and thence vbaciothrough;the tubing; pumps, collecting lines,

etc. In' general We have YfoundV that this procedure suffices. to protect the' entire. system of production and collection againstv corrosion, to asvery, substantial; degree ;A andv far vmore -eiectivelyfthan treatment with: caustic and other'inhibitingf compounds: Which-haya heretofore been4V used. While introduction. of: the.` inhibitor at the Well head usually sutices,.as.hasbeen indicated, it will be obvious that the selected compound may be added to an oil-brine mixture at any point in a systemfwhereits. presence is required to limit corrosiveiacti'on. It will furtherbe noted that We prefer to introduce the inhibitor, in liquid form, as ani aqueous or alcoholic solution for example,

v for greater convenience in handling and soV that it'A maymore readily mixwith. and dissolve in the brine :to` perform its intended function.

The .eiectiveness ofv our inhibitors may be better andmore easily understood by reference to certain tests which 'We have conducted upon natural' oil fieldv brines containing approximately A'dQlllOr-parts-'per million (by weight) of natural saline. solids and about 1,000 parts per million (by Weight) oi hydrogen sulfide, an analysis which is; jtypical off. corrosiute` brines.= produced in `many elds.A Theftestprocedureinvolvedthe'measurement of# the: corrosive` action of` this. brine; alonetaand'` with. o ur; inhibitor fcompoundsg. upon thmr,c u'ghlyv c1eaned^andpolished strips: of cold rolled 'steelmeasuringlxinches x` I6-.18:gauge under conditions which closely. appro'ximatefthose existing. in .aproducing oilwell; .Incarrying out .theltesta-,welledf a seriesof 16* ouncebottles with: natural gas in.V order to exclude.;Y ain.. and to eachfaddeda ,calculated quantity of one of' our amine: reactive finhibitors, and then a measured quantity Lof brineato--make up the: inhibitor .mixtu-re, followingzwhich atestistripofrknown weightv was completely'immersed-in thefm'ixture'and the bottles were sealed with rubber stoppersf to in.- surean airtight'. system; Additional. tests were r-un. in:` other bottles @in which: the.: weighed. test.

strips were immersed in` uninhibitedVv brine; that ist, in.- t'he-hydrogenf sulde containing Lbrin'e just as-.taken :fromi ani. oil well. lAll n of: thel tests were rnnf in..multiple, both for` the-inhibited. and' the blank..,solutions;.` ini order'to avoid theV anomalies offltestingf- Atsthelen'diof a test period'ol about two: Weeks, the testistripsnwere removed from-1 the Y bottles rinsed withtwaiten. and were -l thenn dipped ini I; per.l cent: hydrochloric"I acid:4 solutionforteny water, dried and weighed to determine the sharply less. These test data were used to determine the protection numbers, i. e., the ratio of loss of weight of a strip subjected to an unin-'1 hibited brine to the loss of Weight of a strip subjected to the same brine containing `our inhibitor, which are reported below in the third column of Table I. For purposes of comparison, we then assumed a weight loss of 100 mg. for the uninhibited strip test, and corrected the actual weight losses suffered by the test strips subjected to thev inhibited brines to this assumed basis, thus giving the several weight losses set forth in the fourth column of the table.

The results of these tests clearly indicate that our various inhibitors have a marked eifect in reducing metal loss by the corrosive action of hydrogen sulfide containing brines. Since these tests were carried out under conditions closely approximating those existing in actual Wells, they demonstrate the inhibiting effect which the agents have in protecting oil well tubing, etc., under actual producing conditions.

1 Reaction product of diethanolamine (2 mols) and formaldehyde mol 2 Reaction product of ethylene diamine (1 mol) and formaldehyde mols 3 Reaction product of monoethanolamine (l mol) and formaldehyde (1 mol).

The reaction between formaldehyde and the amines to give the reaction products specified above is Well known, and the method of preparing these products is given in Formaldehyde, by J. F. Walker, A. C. S. Monograph Series No.` 98, Reinhold Publishing Corporation, New York, 1944, pages 200 to 202.

It will be observed that the foregoing series of tests were carried out in solutions containing 62 1A.; parts of inhibitor compound per million parts of brine, thus giving a basis for evaluating the effectiveness of one inhibitor with respect to an` other. The protecting effectiveness of any 'of these agents may be varied, however, by increasing or decreasing the amount employed in the treating process.

It may be noted that brines taken from diiferent Wells, even though containing about the same concentration of salt and hydrogen suliide, may be more or less destructive in their eifects upon oil handling equipment. In using our inhibitors, therefore, We find it desirable to adjust the proportion employed in accordance with the corrosive character of the brine under treatment. As a general rule, We find that from about to 250 parts (by weight) of inhibitor, per million parts (by Weight) of brine, is sufficient to assure highly satisfactory protection under normal operating conditions.

At the conclusion Iof the foregoing tests, and others which need not be speciiically considered, it was observed that the metal strips"-exposed to the uninhibited brines were coated with a thin, fiocculent, gray-to-black material. Doubtless this coating has some effect in protecting theLunderlying metal and slowing down corrosive action. It cannot be of any great protection value, however, because of its tendency to iiake on as is evidenced by the fact that the uninhibited brines were turbid with a grayish occulent precipitate, even thoughthey had been standing in a quiet state' for approximately two weeks. By way.l of

' contrast, the metal strips subjected to the brines containing our amino-reactive inhibitors de` veloped thinbut highly tenacious coating which appear to be particularly resistant to hydrogen Y sulfide brine reaction.

Some evidence of the resistant character of these-films is to be found in the fact that a tenminute treatment in 1 per cent hydrochloric acid did not effect complete removal in many'cases,

and that they were not immediately affected byl organic solvents such as alcohol, acetone, ether, methyl ethyl ketone, gasoline, benzene, toluene, carbon tetrachloride. and similar solvents.

w The inhibiting action of the amino-reactive compounds is not fully understood but one aspect of theV action, and the successful protection of metal against substantial corrosion, certainly appears to lie in the formation of a protecting lm upon the metal, as described above. These films may be complex organic products developed by the action of the inhibiting agent or its interaction with a portion of the hydrogen sulfide and brine, in the presence of metal. They certainly are not the result of mere neutralization of the hydrogen sulfide, as is evidenced by the presence of a high concentration of that' ingredient in the treatedbrines. It may be possible, however, that the inhibitor reduces the activity of the hydrogen sulfide, and other corrosive constituents of the brine. Whatever the nature of the action may be, these facts remain clear: A iilm is built up on metal surfaces brought into contact with hydrogen sulde containing brines which have been treated with amino-'reactive 'compounds in accordance with our invention; and those filmsare resistant bothto mechanical abrasion and chemical reaction; and that the presence of the compounds in such brines does very materially inhibit corrosion of Well tubing, casings, and other oil field equipment Vcarrying the treated brines. 1

It will be observed that the inhibitor compounds are readily obtainable in high concentration, which permits economical shipment and handling both in transit and in the field.

It is to be understood that our improved process isv not conned to the use of only one of the inhibiting compounds referred to but the various mixtures of the inhibitors may be used in a single operation within the spirit and vscope of our invention. Furthermore these corrosion reducing agents may be used alone, or with any other oil Well treating compounds such as those which are conventionally employed for breaking emulsions, limiting scale formation, and the like.

Having described our invention and illustrated it by way of specific examples, what we claim as new and useful is: Y

l. The process of inhibiting corrosion of metal oil Well equipment which comprises introducing into an oil well brine containing Ydissolved hydrogen sulfide, at a point near a producing ho- 5 v rizon of the well, a, ema-11 proportion o! the reac- REFERENCES CITED tkm Produ@ 0f one m01 0f monoethanol amm@ v, The following references are of record in the and one :moi of formaldehyde, the quantity ofc. fue of this patent: the reaction product being sufcient to substantially inhibit corrosion of the metal equipment 5' UNITED STATES PATENTS and thereafter causing the brine to fiow in contact with-the metal surfaces to be protected. Iurg, Calgn; a1 Aua e1930 2. The method according to claim 1 in which 1'847711 Calcott et a] :l Man 1 1932 the reaction product is introduced into the brine 1983584 Damal et aL. nn-, Jam 22 1935 in theammt 0f from am 15 t0 about 250 1 2'268'608 McNulty en lll: Jan. 6'1942 parts by'weight of the reaction product per nil- 4261313 Menaul Aug. 26', 1947 lion part by vWeight of brine.

' MELVIN I. MOYER;

JOSEPH M. HERSH. 

1. THE PROCESS OF INHIBITING CORROSION OF METAL OIL WELL EQUIPMENT WHICH COMPRISES INTRODUCING INTO AN OIL WELL BRINE CONTAINING DISSOLVED HYDROGEN SULFIDE, AT A POINT NEAR A PRODUCING HORIZON OF THE WELL, A SMALL PROPORTION OF THE REACTION PRODUCT OF ONE MOL OF MONOETHANOL AMINE AND ONE MOL OF FORMALDEHYDE, THE QUANTITY OF THE REACTION PRODUCT BEING SUFFICIENT TO SUBSTANTIALLY INHIBIT CORROSION OF THE METAL EQUIPMENT AND THEREAFTER CAUSING THE BRINE TO FLOW IN CONTACT WITH THE METAL SURFACES TO BE PROTECTED. 